On 2021-08-17 14:23, Justin Parisi wrote:
> Referrals probably have the same issue. Will need to test when I get back
> into the office.
Unless you seek to eliminate/avoid, all CI (Cluster Interconnect) traffic at
all cost, I don't really see that that fact matters too much [at mount time].
(Good point about FlexGroups though... I don't have a good solid solution
for those scenarios)
We have since long (years) strived to avoid CI traffic as much as we can,
but we're not as diligent anymore. Note: we do *not* use that DNS function
ONTAP has in it which is intended to help spreading all the traffic (mount
from clients) to various LIFs (based on the "load" on the nblades). Again,
this takes place at mount time, once a mounts sits on a LIF it stays there...
That DNS function (it is based on an algorithm using various "weights")
suffers from serious drawbacks in some situations and we can't take that
risk in our environment. Anyone who has seen and experienced a "mount storm"
will know what I mean.
How important locality is (minimal CI traffic) for you I guess can depend a
bit on what model/power of CI switch you have. If there's enough bandwidth
for the workload streams going across it, it only induces a little extra
latency -- that may matter for some workloads, but I'd argue that for most
it won't.
Once you're on CI switch with 100 GbE, my take is that most people don't
have to bother that much about it. With 100 GbE the latency is lower as well
/M
Justin Parisi wrote:
> But referrals only help with initial mount; after the mount is established,
> the connections stay where they were established. If a volume moves to a new
> node, that doesn't keep locality. They're also not much help with FlexGroup
> volumes.
>